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            <div id="ConfluenceContent"><h3 id="Logging-Loggingsupport">Logging support</h3><p>XWork provides its own layer to support logging - it allows to use many different implementations.</p><p>Currently XWork provides support for the following libraries (in that order base on classpath discovery):</p><ul class="alternate"><li>Commons Logging</li><li><a shape="rect" class="external-link" href="http://www.slf4j.org/" rel="nofollow">SLF4J</a></li><li><a shape="rect" class="external-link" href="http://logging.apache.org/log4j/2.x/">Log4j2</a></li><li>JDK Logger</li></ul><h4 id="Logging-Usage">Usage</h4><p>To use given type of library add it as a Maven dependency or drop into WEB-INF/lib folder. XWork LoggerFactory class will use given logging provider if available.</p><p>To add logging to your application simply declare a Logger as follow:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

public class MyAction {

    private static final Logger LOG = LoggerFactory.getLogger(MyAction.class);

    private String userName;

    public String execute() {
        LOG.debug("MyAction executed with UserName [#0]", userName);
        return "success";
    }

    // getter / setter

}
</pre>
</div></div><h4 id="Logging-Implementingmyownfactory">Implementing my own factory</h4><p>You plug in your own logging solution, simple extend LoggerFactory class and provide a delegate which implements Logger interface, like below:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>JdkLoggerFactory which adds support for JDK logging</b></div><div class="codeContent panelContent pdl">
<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

/**
 * Creates jdk loggers
 */
public class JdkLoggerFactory extends LoggerFactory {

    @Override
    protected Logger getLoggerImpl(Class&lt;?&gt; cls) {
        return new JdkLogger(java.util.logging.Logger.getLogger(cls.getName()));
    }
    
    @Override
    protected Logger getLoggerImpl(String name) {
        return new JdkLogger(java.util.logging.Logger.getLogger(name));
    }
}
</pre>
</div></div><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>JdkLogger is a wrapper around java.util.logging.Logger and implements Logger interface</b></div><div class="codeContent panelContent pdl">
<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerUtils;

import java.util.logging.Level;

/**
 * Delegates to jdk logger.  Maps fatal to Level.SEVERE along with error.
 */
public class JdkLogger implements Logger {
    
    private java.util.logging.Logger log;
    
    public JdkLogger(java.util.logging.Logger log) {
        this.log = log;
    }

    public void error(String msg, String... args) {
        log.log(Level.SEVERE, LoggerUtils.format(msg, args));
    }

    public void error(String msg, Throwable ex, String... args) {
        log.log(Level.SEVERE, LoggerUtils.format(msg, args), ex);
    }
    
    ...
}
</pre>
</div></div><p>Check <a shape="rect" class="external-link" href="http://struts.apache.org/2.x/xwork-core/apidocs/com/opensymphony/xwork2/util/logging/package-summary.html">the source code</a> to see more details.</p><h4 id="Logging-Definingwhichfactorytouse">Defining which factory to use</h4><p>Now you must tell XWork/Struts2 to use your implementation, just define system property like below:</p><p><code>-Dxwork.loggerFactory=com.demo.MyLoggerFactory</code></p><p>you can use the same to explicit tell the framework which implementation to use and don't depend on class discovery, eg.:</p><p><code>-Dxwork.loggerFactory=com.opensymphony.xwork2.util.logging.slf4j.Slf4jLoggerFactory</code></p><p><code>or</code></p><p><code><code>-Dxwork.loggerFactory=<span style="color: rgb(0,0,0);">com</span>.opensymphony.xwork2.util.logging.log4j2.Log4j2LoggerFactory<br clear="none"></code></code></p><p>will enable Slf4j or Log4j2 even if there is commons-logging on classpath available (commons-logging is the first LoggerFactory to look for).</p></div>
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